In general, catheters are used in medical procedures in which tubular structures, lumens, pleural cavities or spaces of the body, such as airways, vessels, organs and joints, are diagnostically examined and/or therapeutically treated. Catheters, which can be introduced into the body through a natural orifice or through an incision, can deliver imaging devices, surgical instruments, implants, fluids, drugs, pharmacologic materials, biologic materials, biologic agents and therapeutics to treat or remedy various pathologies found therein. Catheters also guide and deliver other components, such as guide wires, scaffolds and tools, to the intended site within the body.
Flexible, semi-rigid and rigid endoscopes are widely used in medicine to provide direct visualization for diagnostic and therapeutic purposes. Flexible, semi-rigid and rigid endoscopes are available in many sizes and configurations intended for use in different parts of the body and for a variety of diagnostic and therapeutic procedures. The visualization device (i.e., a fiber optic image bundle or a sensor at the distal tip of the device), together with the means for illumination, are an integral part of the endoscope. Endoscopes may also provide working channels to guide and deliver other instruments to the desired site. Endoscopes and endoscopic systems are, currently, a reusable and expensive resource in a physician's armamentarium. In addition, the endoscopic equipment systems required to operate endoscopes are often large, bulky and relatively immobile devices.
A limitation in the utility of the flexible endoscope is that their outer diameters are often too large, their inner ‘working channel’ diameters are often too small, and their lengths are often inadequate to appropriately diagnose and treat the anatomy and corresponding pathologies found in the far reaches of the body's organs, vessels and spaces. A further limitation of the utility of the flexible endoscope is that the articulation of the distal tip, and thus, its maneuverability, is accomplished through two or more wires that run along the body of the flexible endoscope. These wires are attached to complicated mechanical structures that control the wires in manipulating the flexible endoscope's distal tip. As such, the maneuverability is limited by the capabilities of the mechanical structures that control the wire. In addition, optimizing the external and internal diameters of the flexible endoscope is limited by the size and requirements of the wires and their associated mechanical structures.
Additionally, complications sometimes arise when a flexible endoscope malfunctions and it becomes difficult to remove the flexible endoscope from the body.
Many flexible, semi-rigid and rigid endoscopes have openings, or channels, that run through the elongated body of the endoscope. It is through these channels that catheters, in addition to other instruments and devices, are often placed to provide delivery of various therapeutic remedies to treat the anatomy and pathology found therein.
In many cases, catheters are used independent of direct visualization. In these cases, catheters are usually placed in the body using indirect visualization, such as radiography or fluoroscopy. These indirectly visualized catheters are typically used to reach the human heart and the coronary arteries. Here, guide wires, guiding catheters, and catheters with pre-shaped distal tips, some of which are inserted within one another in the effort to reach the desired location within the heart and the coronary arteries, are used. While these devices come in many sizes and lengths, they are made specific to a particular location within the body that is the targeted diagnosis and treatment site. Moreover, in these methods, the articulation of the distal tip is not independent of the body location and the catheter does not have specific controls at the proximal end to sufficiently control or modify the articulation at the distal tip. Consequently, the navigation and maneuverability of catheters requires great skill, relegating their utility and functionality to the experience and competence of the user.
Accordingly, a new class of steerable catheters has been suggested, such as that disclosed in U.S. Pat. No. 7,608,056 to Kennedy, II. Kennedy II discloses a steerable, fluid forced catheter adapted with a tool receiving passageway or working channel, where the distal portion of the catheter body is tapered. The distal end is steered by way of at least one chamber body having a proximal opening and terminating at an occluded distal end, which is offset from the radial central longitudinal axis and positioned within the catheter. The channel body may be operatively coupled to a fluid actuator for injecting and withdrawing fluids to articulate the end portion and steering tip of the catheter through increase and decrease in pressure within the working channel. Radial compression resistant reinforcements (core plug/filler) within the distal end or steerable tip portion inhibit radial inward expansion (ballooning) of the occluded end of a steering channel caused by a change in internal pressure of one or more chamber body occluded ends. Thus, the catheter is steered by axial stretching of the occluded end of channel body(ies) to achieve bending positions ranging from 1 to 15 degrees.
However, this particular device and method suffers from a number of disadvantages and shortcomings. Significantly, the catheter is limited to bending angles of only 1 to 15 degrees, and a vacuum or negative pressure of some type would be required to achieve bending at the higher end of this bending range. Further, the distal steering tip is limited to bending in the axial plane.
U.S. Patent Application Publication No. 2010/0010437 to Miles also discloses a steerable catheter tip with one or more steering lumens each offset from the longitudinal axis of the catheter body. Increasing the internal pressure of one or more of the steering lumens using a pressure source or heating a thermally expansive material in the steering lumen operates to curl the longitudinal axis of the elastomeric cylindrical body. The inner radial wall thickness between each of the steering lumens and the central lumen is greater than the outer radial wall thickness between each of the steering lumens and an outer surface of the tubular sidewall to ensure greater relative expansion along the radially outer region of the sidewall than the radially inner region in order to cause curling towards the direction of the pressurized lumen. As a result, the catheter bends towards the internally pressurized steering lumen(s) for steering the catheter tip, rather than away from the lumen as taught by Kennedy, II.
Thus, it is unclear whether the distal tip of Miles has suitable elasticity and Young's modulus to achieve maximum bend of the distal tip without deformation or fatigue, or whether it has suitable memory to regain and maintain the steerable catheter's elongation and linear rigidity after bending the distal tip and after repetitive bending of the distal tip. It is also unclear if the tip is capable of tight turns of up to 150 degrees.
A further disadvantage of both of the above steerable catheters is that, when an imaging device is employed to help steer the catheter, such as an image fiber or image sensor, there is no mechanism for cleaning the device when it is retracted into the catheter after having been extended out into the bodily cavity.
What is desired, therefore, is a steerable catheter that can be operated using fluid pressure and/or vacuum. What is also desired is steerable catheter that is able to make very tight turns with a short, steerable distal section and where the diameter of the catheter is as small as possible. What is also desired is a steerable catheter with a mechanism for cleaning an imaging device, such as an image fiber or image sensor, that is used to help steer the catheter. What is further desired is to have the above described catheter that can be manufactured at low cost as a disposable product.